Fuel and speed control apparatus for internal-combustion engines



A. M. PRI-:N-rlss 2,691,268 FUEL AND SPEED CONTROL APPARATUS FOR INTERNAL-COMBUSTION ENGINES 2 Sheets-Sheet l Oct. l2, 1954 Filed Jan. 14. 1949 @www k @L INV-ENTOR oct. 12, 1954 A M. PRENT|S5 2,691,268 FUEL AND SPEED CONTROL APPARATUS FOR INTERNAL-COMBUSTION ENGINES Filed Jan. 14. 1949 2 Sheets-Sheet 2 INVENTOR Patented Oct. 12, 1954 FUEL AND SPEED CONTROL APPARATUS FOR INTERNAL-COMBUSTION ENGINES Augustin M. Prentiss, Hartford, Conn., assignor to Niles-Bement-Pond Company, West Hartford, Conn., a corporation of New Jersey Application January 14, 1949, Serial No. 71,007

(Cl. (iO-39.28)

38 Claims.

This invention relates to fuel and speed control apparatus for internal combustion engines and is more particularly applicable to gas turbine and jet engines suitable for propeller-propulsion, jet-propulsion, or propeller-and-jet propulsion of aircraft. Such engines usually include an air inlet, an air compressor, one or more combustion chambers, a gas turbine, and a tail pipe for discharging combustion gases to the atmosphere. Associated with the engine is a fuel system including a fuel pump for delivering fuel to the combustion chambers. My invention concerns apparatus to control the engine speed and power by controlling the fuel delivery as a function of several Variables including engine speed, engine temperature, other engine operating conditions, and manual control.

Owing to structural and metallurgical restrictions, engines of the type referred to may not be safely operated at speeds or temperatures exceeding predetermined limiting values, but for maximum economy of operation, both speed and temperature of the engine must be maintained at or near these values. On the other hand, engine speed is a critical factor in flight performance or aircraft and an engine may not be used at maximum allowable speed in all flight maneuvers, at all flight speeds, or under all flight conditions. In multiple engine installations, it is often preferable to operate one or more engines at substantially full speed and power while variations in the total power output are obtained by controlling that of one engine, rather than to operate all engines at correspondingly reduced speed and power. Fuel control apparatus must be provided which enables the operator to vary the engine speed as desired for a minimum Value at starting speed and minimum power to the predetermined limiting speed and full power. The control of engine temperature is preferably a substantially automatic function of the fuel control apparatus.

The value of engine speed corresponding to any given value of fuel ow varies as a function of the altitude of flight, flight speed, air 'density at the engine air inlet, engine torque, fuel quality and a wide variety of other factors. For precise regulation of engine speed, or to avoid excessive temperatures, therefore, it is not feasible to rely solely upon automatic regulation of fuel flow as a function of variables which exclude engine speed and temperature.

Objects of my invention are:

(l) To provide improved fuel and speed control apparatus for an internal combustion engine employing four component coordinated fluid pressure systems for regulating the fuel delivery, said systems being respectively responsive to manual control and to engine pressure, temperature, and speed conditions;

(2) To provide in such apparatus improved cam and lever mechanism for modifying the operation of the manual system by the pressure responsive systems;

(3) To provide improved pressure regulating and pressure responsive control elements which may be used in fluid pressure apparatus such as above described;

(4) To provide a simplified fuel and speed control apparatus, wherein all of the control elements operate coordinately to control a single flow regulating valve which functions under a constant pressure head and varies the fuel flow by varying the opening through said valve;

(-5) To provide apparatus such as described, wherein the liquid fuel is utilized as the principal operating iluid of the control elements, thus eliminating the necessity for separate oil pressure systems heretofore employed;

(6) `To provide an improved arrangement of external connections to such apparatus including a main drive shaft for simultaneously rotating Vthe several control elements, and a speed governor means, and a mainV control shaft having adjacently thereon a pair of cams for operation of the manual and speed control systems;

(7) To provide in such apparatus improved means for controlling acceleration and deceleration of the engine as a function of the pressure responsive system; and

(8') To provide improved means responsive to the control shaft for predetermining the engine speed including adjustable means for preselecting a maximum value of speed independently of operation of the control shafts.

Other objects and advantages of my invention will become apparent from al consideration of the appended specification, claims, and drawings, in which:

Figure l shows, somewhat diagrammatically, an engine suitable for propeller-and-jet propulsion of aircraft, together with its associated fuel and speed control apparatus and engine control lever; there being also shown principal connections between the engine and a diagrammatic illustration of the fuel and speed control apparatus of Fig. 2; y

Figure 2 shows, also somewhat diagrammatically, fuel and speed control apparatus embodying the principles of my invention.

Figure 1 Referring to the drawing, Fig. 1, there are shown the principal elements of the engine above referred to, a supporting casing lil, an air inlet I2, a multistage compressor I 4l, a compressor rotor shaft l, one each of a number of combustion chambers i8, one of a corresponding number of fuel discharge nozzles 20 connected to a generally circular manifold 22 by means of a conduit 24; a multistage turbine 26, a turbine rotor shaft 28 connected to the compressor rotor shaft i6, a tail pipe 33 for discharging combustion gases from turbine 26; a center "bearing 32 and end bearings 313 and 3G supported by casing Hl, a propeller shaft 38 to which is fixed a propeller 4Q, and a gear train Ll2 connecting shafts t6 and 38 for rotating propeller E at a speed proportional to engine speed and for operating the fuel pump and other accessories. Construction of a jet engine used solely for jet propulsion is similar to that of the engine of Fig. 1 except for omission of the propeller and propeller shaft and corresponding modification of the gear train. Since, in a jet engine, the power developed by the turbine is used only for operating the compressor and accessories, single-stage rather than multi-stage turbine construction is generallyr employed.

A fuel pump 44 is connected to a pump inlet conduit 46 leading from a source of fuel supply (not shown) and to a pump discharge conduit 48. Fuel ows from the indicated source of suppiy through inlet conduit 46, pump 44, and pump discharge conduit 48, fuel control apparatus 59, and conduit 52 to manifold 22 in the engine. Pump 44 is of the high pressure, constant delivery type and is operated by a drive shaft 45 connected to gear train 42 in the engine, or any other suitable source of power.

In each of the discharge nozzles 2B there is a series of fixed slots, one of which is indicated at 2l, through which fuel enters the nozzles from conduits 24. The fuel iiow from the nozzles is directly proportional to the effective area of slots '2l and is a square root function of the drop across the slots between the pressure in conduits 24, which is substantially equal to the pressure (pF) in conduit 52, and the pressure in the combustionchamber. It follows, therefore, that the fuel delivery to the'combustion chamber is a function of the pressure (pF) in conduit 52 which is controlled by fuel control apparatus D as hereinafter described.

When it is desired to limit the range of fuel pressure so that its value at maximum fuel flow is less than that corresponding to the square root function of the drop across slots 2i, the nozzles may be provided with auxiliary slots supplied by another manifold connected to conduit 52 through a pressure-responsive flow-divider which opens at a predetermined value of the pressure (pF). In this manner the pressure (pF) may be maintained suiciently high to produce satisfactory nozzle discharge without requiring the control apparatus to operate under unfavorable pressure conditions at maximum flow.

The control apparatus of Fig. 2, diagrammatically shown in Fig. 1, is connected to a source of compressor discharge pressure (pn) in the engine by a conduit 54 and, as subsequently explained, the control apparatus is responsive to the absolute compressor discharge pressure (pn) which is an indication of air flow through the engine. The value of (pD) increases as the engine speed increases, as flight speed increases, and

as the altitude of flight or entering air temperature decreases, and is also a function of the compressor characteristics.

A main drive shaft 58 in the control apparatus is driven by the engine at a speed proportional to engine speed and a main control shaft 60 is rotatable in response to movement of a shaft 62 to which is fixed an engine control lever 64. Control lever 66 is manually operable in reference to a scale 68 on a xed quadrant 66, scale 6B being calibrated in terms of R. P. M. engine speed.

Referring to Fig. 2, there is shown, somewhat diagrammatically, an embodiment of my invention, all principal elements of which, except a thermal control l5, are enclosed in a casing 'l2 having external connections with conduit 54 for supplying air to the apparatus at the compressor discharge pressure (pD), with conduit 48 for supplying fuel under high pressure to the control apparatus, with conduit 49 for the return of excess fuel to the inlet conduit e6, and with conduit T3 for the return of fuel from the interior of casing l2 to the source of fuel supply (not shown). Casing 12 as shown in the drawing is of continuous cross-section but for purposes of manufacture and assembly may be made in an equivalent form comprising two or more separable elements secured to each other by bolts and gaskets in the conventional manner.

The control apparatus of Fig. 2 is a self-contained fluid pressure system employing the interior of casing l2 as a reservoir is which is maintained approximately full of liquid fuel .at the pressure (p) in order to permit the working elements to operate in a liquid bath and which is vented at a threaded port 'i6 to the fuel supply source. If desired, reservoir 14 may be made a part of the oil system of the engine. In this case, a pair of plugs 18 and 8B, otherwise serving as drain plugs, are removed from casing 'l2 and the respective casing openings are then connected by suitable inlet and outlet conduits to the engine oil system. Also, the lower end of drain conduit 'i3 is plugged and conduits |38, |64, 56 and S (described hereinafter) are connected by drain pipes to the fuel supply source.

Fuel pump 44 draws liquid fuel under a low pressure (p) (e. g. 10 pounds per square inch) from a supply source (not shown) through inlet conduit 46 and discharges said fuel under a high pressure (p1) (e. g. 50-600 pounds per square inch) through discharge conduit 48 into a passageway 52 in the lower .part of casing l2.. Passageway 82 communicates through orifices 84 and 85, controlled by a balanced valve 83, with a chamber ed which is connected by a passageway 92 to fuel dischargeV conduit 52 leading to fuel nozzles 2D in combustion chamber it. A vcheck valve Q4 at the junction of passageway 92 and conduit 52 is biased toward its seat by a spring 96 and adjustable plug S8 and maintains a small (e. g. 20 pounds per square inch) vconstant lpressure drop (pz-p3) between the fuel in passageway 92 and conduit 52 and prevents the escape of fuel from chamber 9G when the -engine is not in operation and insures that the pressure (p2) in chamber 9B will never be less than the pressure (p) in inlet conduit It. Valve 38 is biased toward its seat by a spring 89.

Communicating with passageway 82 is a branch passageway l in which is seated a valve sleeve |02 having a plurality of ports m4 which communicate with conduit is leading to fuel inlet conduit '46. Mounted in sleeve |02 is a piston valve 06 which is biased in a closing direction by a spring |08 seated on an `adjustable stem ||0 'and locked in adjusted position by a lock nut ||2. Stem I| 0 extends toward the upper end -of spring |08 so as to limit the maximum downrection on valve v|06 is always the same as the pressure (p2) in chamber 90. -A lter |28, 'seated on an adjustable vplug |22, in passageway i8 prevents any particles of dirt in the fuel in chamber .90 from entering valve'sleeve |82 and causing fvalve |06 to bind or stick.

Since the upper and lower areas (A) of valve l|06 are equal, the net force acting in said valve is equal to the fuel pressure differential (p1-pz), times the area (A) of valve |06, minus the force (S) of spring. |08. Hence, the fuel pressure differential (101-292)=S/A, and since (A) is constant, the fuel pressure differential (pr-p2) is proportional to theforce (S) of spring |88, which is determined by the adjustment of stem lill. In practice, the tension of spring 88 is adjusted to maintain a fuel pressure differential (prwpz) of approximately 20 pounds per square inch which is always constant, irrespective of the variation in inlet pressure (p1) which may vary between wide limits (i. e., 50-600 pounds per square inch), depending upon the conditions of operation of the engine. Thus, the fuel metering head on valve 88 is always constant under all conditions `of operation, and the rate of fuel ilow to the engine is determined by the degree of opening of valve 88. When the fuel discharged by pump 44 is more than that required by the engine, as determined by the opening of valve 88, the excess fuel is returned to the inlet side of the pump through valve |06 and conduit 48. In order to insure a close control of the pressure dilferential (p1-p2), Valve ports |04 are preferably made elliptical in shape with their major axes horizontal, so that the opening of ports |64 by valve |06 is an elliptical function of the travel of said valve.

The control apparatus comprises four mechanically and hydraulically cooperative component systems, as brieiiy outlined in the immediately following numbered paragraphs, for regulating the variable control pressure (pc) which acts on valve 88 to control the full flow to the engine, namely:

(1) A manual control system principally including a. main servo valve |24, a main servo valve sleeve |26, a main power piston |28, a main floating lever |26, a push rod |30, Ed" a, cam |32 exec to the main Control shaft 60, for rendering pressure (pe) variable by movement of the engine control lever 64, Fig. 1. Also included in the manual control system, Ias set forth herein, is a lever mechanism |34 comprising a pair of levers 282 and 286, a circular bearing 208 between said levers, a spring 2|4, and a rod 200 for loading piston |28 with a force due to spring 2|41 Fluid flows discontinuously to the manual control system through a conduit |36 connected to main fuel passageway 82 and is drained from the manual control system through an outlet passage |38 opening into reservoir 14 at the upper end of valve sleeve |26. The variable `A6 control pressure (pc) is transmitted from the manual control system through a conduit |40 which is connected to control cylinder |42.

(2) A barometric control system principally including a barometric servo valve |44, av barometric servo valve sleeve |46, a barometric power piston |48, a barometric floating lever |58, a fixed elongated barometric cam |52, a positioning bar |54 for varying the position of bearing 208, and a pair of bellows |56 and |58, the' former being connected to aA conduit |60 and the latter being evacuated to zero pressure (po) and sealed. The control pressure (pe) is made a function of the absolute compressor discharge pressure (21D) by transmission of movement of piston |48 through cam |52, 'and positioning bar |54, of lever mechanism |34 to the main power piston |23 in the manual -control system. Fluid flows discontinuously to the barometric control system from the main fuel passageway 82 through a conduit |62 and is drained from the barometric control systemthrough one or the other of two outlet passages |64 and |66 in sleeve |46, which` passages open into reservoir 14.

Y(3) A speed control system principally including a governor valve mechanism generally indicated at |68, a valve setting lever 18 and a cam |12 on themain'control shaft 66. In this system, the control pressure (pc) is made a function of the engine speed by modifying movement of the floating lever |58 of the barometric control system inv response tomodiiication of the compressor discharge pressure in bellows |56 as a function of the engine speed.

(4) .A thermal control system including the thermal control 18 for overriding the speed'con" trol system as a function of the engine temperaf ture. Normally, there is no dow of fluid through the thermal control system, but when the predetermined limiting or maximum allowable ternperature is exceeded air flows from conduit |88, successively through a connecting conduit |14, past a control valve in thermal control 10, to the outside atmosphere. This reduces the compres-l sor discharge pressure in bellows |56, as a function of engine temperature, in the same manner as the speed control mentioned above, whenever the engine temperature exceeds a maximum allowable limit.

Manual control system A wall |16 separates the reservoir 14 from the fuel now channels82, and 92 and is suitably bored or otherwise machined for housing and opz eration therein of some elements of the component control systems previously defined.

"Inthe" manual control system, a gear |18 is provided at the top of main servo valve sleeve 26 for rotation of the lsleeve in wall |16, sleeve |26 being installed with gear |18 above wall |16 and having its upper end extending somewhat beyond the upper side of the wall. f Gear |18 and hence sleeve |26 are rotated by another gear |80 fixed to a shaft |82 which'in turn is driven from the mainrdrive shaft 58 through a suitable connection (not shown). Similarly, a gear |84 is provided at the-upper end of piston |28 which is both slidably and rotatably operable in wall |16 and is installed with gear |84 above the wall. Gear |84 is rotated by gear |80. Any other means of suitably rotating sleeve |26 and piston |28 may be employed, the purpose of such rotation being to avoid sticking of the main servo valve |24 in sleeve |26 and to prevent sticking of the piston |28 in wall |16.

i `7 Valve sleeve |26 providedwithal pair of parallel circumferential grooves |88 and |88 and one .or more corresponding ports |90 and |92 drilled radially at the horizontal centers of the grooves. The upper end of conduit |353 opens opposite groove |86 and ports |88 are therefore continuously supplied with uid at pressure (p1) Groove |88 and ports |92 are similarly connected to the upper end of a passage |40 which communicates with cylinder |42.

Valve |24 is undercut to form an annular chamberA 94 and has a neutral position as shown in Fig. 2 in which the lower edge of the undercut is alined with the upper edge of port |E0, and the upper edge of the undercut is alined with the lower edge of outlet passage |38. Ports |92 communicate with chamber |94 regardless of the position of valve |24 in its normal range of operation. When valve |24 is displaced downward so that port |88 -opens into chamber |84, a path for flow is provided which successively includes conduit |38, groove |88, ports |90, chamber |94, ports |92, groove |88, passage |48, and an expansible chamber |42 included between the lower end of piston |28 and the upper end of piston |88. rPhe value of the variable control pressure (pc) in chamber |42 is thus increased upon downward movement of valve |24 from its neutral position. Similarly, when valve |24 is displacedupward so that chamber |94 opens into outlet passage |38, a path for flow is provided from chamber |42, through passage |48, groove |88, ports |82, chamber |94 and outlet passage |38 to reservoir 14, the pressure (pc) being thereby decreased.

The left-hand end of main floating lever |28 has a pin-.and-slot connection |98 with rod 200 which has a self-alining connectin at its lower end with the bored interior of piston |28 so that upward movement of the piston lifts rod 200 and simultaneously allows angular displacement of the rod with respect to the piston without causing the latter to bind in wall H0. The upper end of rod 200 is hinged to the left-hand end of lever 202 in mechanism |34, lever 200 having its right-hand end hinged to a xed support 284. Above lever 202, mechanism |34 includes the lever 208 which has its left-hand end hinged at a pin 2|0 fixed. in a support 2|2 above and approximately on the centerline of piston |28. The right-hand end of lever 208 is connected to tension spring 2 |4 which has its lower end anchored in ai xed support 2 6. A measure of the downward force of spring 2 I4 is transmitted from lever 208 to `lever 202 through the circular bearing 20B the position of which is regarded as xed in thev present discussion.

Piston |28 is subjected to an upward force` proportional to the diiferential (e-p) between the respective pressures` in chamber |42 and reservoir '|4- vand to a measure of the downward force of spring 2 I4 which is transmitted to the piston through lever mechanism |34 and rod 200. The rate of spring 244 is high, so that thevalue of the differential (pc-i0) and hence the variable control pressure (pe) may vary throughout a wide range of values corresponding to a relatively narrow range of movement of the piston which is positioned to maintain the forces acting thereon in equilibrium.

Main floating lever |28 is positioned by: (l) push rod |30 which carries an arm 218 engaging an adjusting screw 2 I8 threaded through lever |28 and. locked in place by means of a nut 228; 2) rod 200 which serves as a pivotal support for' the lefthand end of lever |28; and (3) a light spring 22-2 compressed between a fixed support 224 and a -groove 234 and ports 236.

retainer 226 supported by the upper end of valve |24, which causes the adjusting screw 2|8 and hence lever |28 to follow movement of push rod |30 as the latter is actuated by cam |32. I-t is noted from the above that, excepting the substantially negligible force due vto spring 222, the main servo valve |24 does not directly effect the position of lever |28 but instead is positioned by the lever, there being equal and opposite forces proportional to pressure (20) on both ends of valve |24, by virtue of communication between reservoir 14 and the bottom end of sleeve |26, through passageway 228, chamber 230, passageway 232, When considering the manual control system only, the position of bearing 208 and hence the downward force of rod 20.0, corresponding to any given position of piston |28, is regarded as iixed. In the neutral position of servo valve |24, as shown in Fig. 2, the manual control system is in a state of equilibrium; i. e., there is no flow of fluid in the system, the pressure (pc) in chamber |42 is such as to maintain piston |20 in a position corresponding to the position of cam |32, with valve |24 in neutral (closed) position, and so that the fuel ow through valve 88 corresponds with the value of pressure (ne) trapped in the system by closure of servo valve |24.

Upon clockwise movement of control lever 64, Fig. l, and consequent clockwise movement of main control sha-ft 88 and cam |32, lever |28 moves clockwise about connection |98 and servo valve |24 is depressed from its neutral position. Consequently, as previously explained, the value of control pressure (pc) and hence the fuel flow to the engine increase. Control pressure (pc) continues to increase until piston |28 responds by raising lever |28 and valve |24 a sufficient amount to restore said valve to its neutral position, following which no further change occurs in the manual control system as long as the position of shaft remains undisturbed. Similarly, upon counter-clockwise movement of control lever 54, Fig. 1, and corresponding counterclockwise movement of shaft B0 and cam |32., lever |28 moves counter-clockwise about its connection with rod 200 and servo valve |24 is elevated above its neutral position. In this case, as previously explained, the value of control pressure (pc) and hence the fuel rlow decrease, continuing to do so until piston |28 responds by lowering rod 200 and lever |28 to a new position .at which servo valve |24 is again restored to its neutral position. When servo valve |24 is in its neutral position, the value of control pressure (pc), and hence the fuel flow, is determined by the position of control shaft 60 for a given xed position of bearing 208 in lever mechanism |34.

As stated earlier, the engine speed corresponding, to any given value of fuel flow varies as a function of entering air density, flight speed, and other factors over which the manual control system has no control and to which it is unresponsive. It follows, therefore, that the manual control system provides a means of regulating the variable control pressure (pc) from minimum to maximum values corresponding to a predetermined range of clockwise movement of the engine control lever 54, Fig. l, and depending upon the downward force transmitted by rod 200 to piston |28.

Bcrometric control system The operationl of lever mechanism |34 and positioning bar |54 and their relation to rod 200 is explained in the following description of the barometric control system and in subsequent explanations of coordinated functions of the barometric and other component systems.

In the barometric control system, the upper end of bellows |56 is nxed inside casing 12 directly over bellows |68 which is of substantially the same eiective area and which has its lower end xed to a portion of wall |16. A rod 240 rigidly connects the free ends of the bellows to each other so that expansionor contraction of either is accompanied by an equal and opposite movement of the other. A cylindrical stop 242 is provided to limit contraction of Abellows |58. Inside bellows |56 and at its upper end there is an adjustable spring support 244 the position of which can be varied as desired by means of a nut 246. Between the lower end of support 244 and the upper end of rod 240 there is a tension spring 248 for biasing t'e bellows and rod assembly upward in opposition to the differential pressure (pn-p). A cover 250 and a gasket 252 are provided for enclosing support 244 and nut 246 which, upon removal of cover 250, are accessible from the exterior of the casing. YThe barometiic lever |50 is hinged at approximately the mid-point of its length on a pin 254 in rod 240, the left end of the lever being connected to the upper end of barometric valve |44 by means of a pin-and-slot connection 256 which permits vertical movement of valve |44 in sleeve |46 as the angular position of lever |60 changes. The right-hand end of lever |50 has a pin-andslot connection 258 with a rod 260 fixed to the barometric power piston |48. The upper end of rod v260 above its connection with lever |50 is hinged to a link 262 which is pivotally connected to the left end of positioning bar |54 by means of a pin 264 on which turns a roller 266 engaged with the fixed barometric cam |52. The position of cam |52 is fixed by a pair of pins 268 and 210 respectively tted into fixed supports 212 and 2|2. The cam is slidable on the pins so that it can be removed from the apparatus for replacement or any other desired purpose. The righthand end of positioning bar |54 has a pin 214 fixed therein on which the circular bearing 208 is mounted. Roller 266 is held in Contact with the upper surface of cam |52 by means of another roller 210 which is rotatable on a pin 218 fixed in a triangular bracket 260. Bracket `280 is pivoted to link 262 and a spring 282, compressed between the link and one side of the bracket, holds roller 216 against the lower side of cam |62. Thus, as rod 260 moves in a vertical direction, link 262 follows so that roller 266 remains in engagement with the contoured upper face of cam 52. Both vertical and angular movement are imparted to link 262 in this process so that: when piston |48 and rod 260 descend, bearing 208 is moved leftward and the downward force on main power piston |28v due to spring 2|4, is increased; and, similarly, when piston |48 and rod 260 rise, bearing 208 is moved rightward and the downward force on the main power piston |28y is decreased.

The barometric servo valve |44 is undercut to provide a pair of annular chambers 284 and 286 between the valve and sleeve 46 in which the valve is slidable. The vertical position of valve sleeve |46 in reference to casing l2 is fixed and the sleeve is rotated by means of a gear 296 driven from main drive shaft 5S through a suitable connection (not shown). The valve sleeve has three pairs of ports, 290, 292 and 294.

In all operating positions of valve |44, ports 10Y 290 open into the annular chamber 284 and ports 294 open into the annular chamber 288. Fluid in chambers' 284 and 286 is maintained at pressures designated (p4) and (ps), respectively, as later explained.

Ports 292 are just closed when valve E44 is in its neutral position, as shown in the drawing, the width of the ports being substantially equal to the Width of the valve land between the lower end of chamber 284 and the upper end of chamber 286. The outlet passage |66 in sleeve |46 is also just closed by the land at the lower end of valve |44 and outlet passage |64 is similarly just closed by the land at the upper end of valve |44, when the latter is in its neutral position.

lPorts 292 are connected to the end of conduit |62 so that the ports 292 are continuously supplied with iiuid at pressure (p1). Ports 294 are connected to one end of a conduit 296 which has its other end connected to an expansible chamber 298 below piston 48. Ports 290 are connected to a pair of conduits 300 and 302. Conduit 302 is connected to a check valve chamber 304 in wall |16 above the barometric power piston |48, for transmitting the pressure (p4) lto chamber 304 from chamber 284. Conduit 300 is supplied with fluid from chamber 284 at pressure (p4) and is intermittently connected by means of a slot 306` on main drive shaft 58 to a conduit 308 for supplying iiuid at a pressure (p5) to a chamber 3| 0 above piston |48. Slot 306 intermittently connects conduits .300 and 308 as it rotates and is descriptively referred to as a chopper valve. It serves to restrict flow between conduits 300 and 308. The area of slot 306 is substantially greater than that of an equivalent fixed restriction between the two conduits. A number of parallel slots may be substituted for the single slot 306, if desired.

When the baometric servo valve |44 is elevated above its neutral position, iiuid is permitted to flow from annular chamber 264 through outlet |64 to reservoir 14, thereby reducing the pressure (p4) in conduit 300 and (p5) in conduit 308. Simultaneously, iiuid is permitted to now from conduit |62, through port 292, chamber 286, and conduit 296 to chamber 298, thereby increasing the pressure (pe) in chamber 298.

When valve |44 is depressed below its neutral position, uid is permitted to now from conduit |62 through port 292, and chamber 284, to conduits 300 and 308, thereby increasing the pressure (p4) in conduit 300 and (p5) in conduit 308. Simultaneously, fluid ows from chamber 286 through outlet |66 to reservoir 14, thereby reducing the value of pressure (p6) in conduit 296 and chamber 3|0.

The position of rod 240, and hence the position of Spin 254, is determined by the pressure differential (pn-po) acting on bellows |56 and |58 and by spring 248, there being a different predetermined position ofthe pin for each value of the differential, at any given nxed position of spring support 244. In steady state operation, when the barometric servo valve |44 is in its neutral position, as shown, the positions of the power piston |48 and of rod 260 are predetermined by the position of fulcrum pin 254 and the pressure differential (pt-p5 acting on piston |48. This diierential has a substantially constant value when the barometric control system is in equilibrium, and equals Zero when the apparatus is constructed so that no force is required to maintain bearing 208 in any fixed position corresponding to a iixed position of pin 254. y

The barometric control system varies the position of power piston 148 and rod ZS to maintain servo valve i413 in its neutral position as the position of fulcrum pin 254 changes in response to changes in the value of the diierential (pn-po). The barometric control system therefore positions bearing 2F38 as a function of the barometric pressure differential. The power for positioning bearing 268 is supplied by the hydraulic system. The downward load on main power piston |23 due to spring 254 is therefore modified in accordance with the barometric pressure differential.

Chamber SIG is connected to check valve chamber 3M by a conduit 312 for iiow from chamber 3 I9, past a ball check valve 3 lll into chamber 338, when the pressure (p) exceeds pressure (p4) in chamber 284 by a small amountpredetermined by a spring 31S which loads the valve. rlhe check valve prevents reverse flow from chamber 28d to conduit 3I2 at all times.

Considering the barometric control system independently of the manual control and other component control systems, when a condition of equilibrium is distributed by an increase in compressor discharge pressure (pn) or in the modified compressor discharge pressure (pM) (hereinafter described), rod 24B and fulcrum pin 254 are lowered to a new position. The right-hand end of barometric noa-ting lever |50 is not affected until pressure changes produced by the valve IM cause movement of piston 148. Downward movement of pin 254. causes downward movement of the servo valve IM and consequent increase of pressure (p4) in chamber 284 and conduits all?. and S as previously explained, and also decrease of pressure (pa) in chamber 285, conduit 296, and chamber 298 below power piston 43. Increaseo pressure (p4) in conduit 369 produces a flow through chopper valve 36S, resulting in a corresponding increase in pressure (p5) in chamber 3HE above the power piston. The rate of change of pressure (p5) is a function of chopper valve 3136. As the diiferential (p5-p6) increases, the barometric power piston |48 moves downward, thereby turning lever d50 clockwise on fulcrum pin 254 and moving servo valve 144 upwards toward its neutral position. The downward movement of piston M8 and rod 25d continues until the neutral position of valve 44 is restored and rod 2t@ is in a new position corresponding to the neutral position of the valve and the new lower position of pin 2Sfl.- When equilibrium occurs, pressures (p5) and (pe) are again substantially constant.

In the above train of events, the particular value acquired by the differential (p5-pe) in restoring valve M4 to its neutral position is not important, since all that is required is that the position of rod 259 corresponds to the neutral position of the valve. If movement of rod 26e is opposed by frictional or other forces, the control operates to vary the differential (p5-ps) sufficiently to compensate such forces. During the process, check valve 3M remains seated, since the pressure (p5) cannot increase above the pressure (214).

When the compressor discharge pressure (po or pM) decreases, with the barometric control system in an initial state of equilibrium, rod 2&8 and pin 254 rise causing clockwise movement of lever |50 about its pivotal connection with rod 26B and raising the servo valve 5M above its neutral position. As previously explained, pressurcs (p4) and (p5) decrease and pressure (pe) increases, thereby causing piston m8, rod 260 and the right-hand end of lever |53 to move upwardly so that the servo valve M15 moves downward toward its neutral position. During this process, decrease in the value of pressure (pi) allows check valve 314 to move leftward, thereby allowing fluid to flow from chamber 3H) so that pressure (p5) decreases more rapidly than would be permitted by reversed flow from conduit 308 through chopper valve 36S. .Hencey rod 26D moves upwardly (in a fuel flow decreasing direction) more rapidly than it moves downwardly (in a fuel ilow increasing direction). Equilibrium of the barometric control system is restored with valve IM in its neutral position, with fulcrum pin 254 in a new higher position, with rod 260 in a corresponding new higher position in which the upward and downward forces on the rod are in equilibrium, and with check valve 3M again seated. .As is apparent from the drawing, when movement of fulcrurn pin 255 displaces the brometric servo valve IM in either direction from its neutral position, the barometric power piston M3 is required to move approximately twice as far in the same direction to restore the valve to its neutral position.

Speed control system Governor valve mechanism IES includes a flyball speed responsive device 3H! operated by the main drive shaft 5S for varying thevertical position of governor valve sleeve 32d as a function of engine speed. The valve sleeve operates in a suitably bored projection 322 or casing 12. The inner race of a ball bearing assembly 32E is fastened to the upper end of sleeve 320 and the outer race of bearing assembly 324 supports a lower governor spring retainer 326 which is slotted so that lever Viti and retainer 325 are independently movable in relation to each other in a vertical plane. When cam H2 on main control shaft 60 is rotated counter-clockwise, it compresses a governor spring 323 between lower retainer 32B and an upper governor spring retainer 33B which is forced upward by spring 328 against the cam V52.

Cam H2 is actuated by movement of the engine control lever 64, Fig. 1, for varying the position of the upper governor spring retainer 330, and hence for varying the load of spring 328 on valve sleeve 326 in opposition to the upward force of the speed responsive device 318. In the particular embodiment shown, the downward force of governor spring 32d varies substantially directly with the spring deliection, while the upward force due to speed responsive device dit is proportional to the square of the engine speed. When these forces are in equilibrium, there is no vertical movement of sleeve 32B. Cam H2 is generated so that as manual control lever 64 is advanced clockwise throughout a predetermined range in reference to the uniformly calibrated R. P. M. scale BB, Fig. l, the deflection of spring 322 is varied at a non-uniform rate so that the speed required to produce a state of equilibrium increases in accordance with the scale value corresponding to the position of the lever.

Slidably mounted in sleeve 320 is a servo valve 332 having upper and lower lands connected to a center land 336i by reduced portions which dene annular chambers 33t and 333 in sleeve 320. The width of land 33@ is such as to just cover a port 3ds in sleeve 320 when said land and port are in alignment. Port 3fm communicates through an annular groove 352 in projection 322 with conduit |60 leading to the interior of bellows |56 in all operating positions of sleeve 320. Chamber 336 communicates through a slot 344 in sleeve 320 and a passageway 346 with the outside atmosphere. Chamber 338 communicates through a slot 348 in sleeve 320 with a conduit 350 which connects with conduit 54 from the compressor discharge chamber of the engine. Valve setting lever |70 pivoted at 354 to casing '|2 has a pin-and-slot connection to valve sleeve 320 and passes through a slot 356 in seat 326 which is of suflicient width and height to permit free movement of seat 326 and sleeve 320 with respect to lever |10. Lever |70 is held in an adjusted position by spring 358 and adjusting screw 360 which is threaded through the casing '|2 and locked in position by lock nut 362. The setting of lever determines the position of valve 332 and hence the point in the travel of sleeve 320 at which land S34 commences to open port 340.

Whenever the downward force of spring 328 equals the upward thrust of the governor fly-ball arms on sleeve 320, as when the engine speed corresponds to the R. P. M. called for by the position of manual control lever 64, sleeve 320 is in its equilibrium position, with port 340 directly opposite and just covered by land 334, as shown in Fig. 2. The speed control system |68 is then cut-out, and the fuel feed to the engine is responsive only to the barometric and thermal control systems. If now the force of spring 328 is increased by a counter-clockwise rotation of cam |12 in response to a movement of control lever 64 to the right, or the upward thrust of the governor fly-balls is reduced by an extraneous reduction in engine speed, so that the force of spring 328 exceeds the upward thrust of the governor fly-balls, sleeve 320 descends, progressively uncovering port 340. This permits compressed air under compressor discharge pressure (pn) to flow through conduit 54, passageway 350, chamber 338, port 340 and conduit |60 to the interior of bellows |56, increasing the downward thrust of said bellows on rod 240 and lever |50, with resulting increase in fuel flow to the engine, as has been previously described. The increased fuel flow causes the engine speed to increase until the R. P. M. again corresponds to that called for by the position of control lever 64, whereupon the upward thrust of the governor fly-balls again equals the force of spring 328, land 334 closes port 340, and speed control system |68 is restored to equilibrium.

`Whenever the upward thrust of the governor lfly-balls exceeds the downward force of spring 328, as when cam |12 is rotated clockwise by a movement of control lever'64 to the left and reduces the compression in spring 328, or the upward thrust of the governor fly-balls is increased by an extraneous increase in engine speed, sleeve 320 moves upwardly, uncovering port 340, which permits compressed air to escape from the interior of bellows |56, through conduit |60, port 340, chamber 336 and conduit 346 to the outside atmosphere. This reduces the pressure in bellows |56, and the downward thrust of said bellows on rod 240 and lever |50, with resulting decrease in fuel flow to the engine, as previously described. The resultant decrease in engine speed continues until the R. P. M. again corresponds to that called for by the position of control lever 64, whereupon the upward thrust of Ythe governor fiy-balls equals the force of spring 328, land 334 closes port 340, and the speed control system |68 is restored to equilibrium.

From the foregoing, it is apparent that the pressure in bellows |56 may vary from a maximum pressure equal to the compressor discharge pressure (pD) to a minimum equal to atmospheric pressure (pA), depending upon the action of the speed control system. Since the pressure inside bellows |56 can never exceed the compressor discharge pressure (pn), the design and adjustment of bellows |56 must be such that with a pressure (10D), it exerts a suiiicient force on the barometric control system to bring the engine to its maximum rated speed when the manual control lever is in its extreme righthand position. Under ordinary conditions of engine operation, the pressure in bellows |56 will have a value (pM) equal to the average between (pD) and (11A), both 0f which vary with engine operating and flight conditions. Thus, both (17D) and (pA) vary directly with speed of flight, and inversely with altitude of flight and atmospheric temperature. (10D) also varies with engine speed and temperature and compressor characteristics.

Coordination of the l systems Both cam |32 in the manual control system and cam |12 in the speed control system are xed to control shaft 60 for simultaneous operation as control lever 64, Fig. l, is advanced clockwise through the predetermined range. In the embodiment shown, the total range of movement of lever 64 is approximately 100.

ln acondition of steady state operation at constant speed and constant fuel flow, the positions of all movable elements in both the manual and the "speed control systems are fixed (except in respect to rotation of the valve sleeves and main power piston |28), main servo valve |24 and governor valve sleeve 320 are in their neutral positions, pressures (pM) and (pc) are substantially constant, and as previously explained and shown in Fig. 2, the right end of main iloating lever |28 is supported by finger 2|6.

When control lever 64 is advanced clockwise fromv the position shown in Fig. 1 to another position within the rst 90 range of movement of the lever, the lift of cam |32 decreases, push rod |30 is lowered, and the right end of main iloating lever ||2 follows the push rod. Simultaneously, with movement of cam |32 however, cam |'|2 also turns counterclockwise to compress spring 328. The downward force of spring 328 is thus increased and governor valve sleeve 320 is depressed from its neutral position in respect to land 334 of valve 332 so that compressed air iiows from conduit 54 through conduit 350, and port 340 to the interior of bellows |56, thereby increasing pressure (pD or pM) in bellows 56. Servo valve |44 and consequently piston |48 move downward, depressing main floating lever |28,

thereby rendered maximum during acceleration manual and speed controlL of the engine. The maximum fuel flow during periods of acceleration is determined by the position of control lever 64 acting through cam |32, and not by the difference between actual speed and desired speed. This limitation of the fuel flow during acceleration is necessary to prevent overheating of the engine. v

As the engine speed increases, governor valv sleeve 320 continues to rise until the engine speed attains the desired speed corresponding to the position of lever 64, whereupon port 340 is closed by valve 332. Simultaneously, the increasing pressure (pc) in chamber |42 causes piston |28 to rise to a new position, corresponding to the new position of push rod |30 and finger 2 6, which returns valve |24 to its neutral position, whereupon the whole control apparatus is restored to equilibrium and a steady state of engine operation ensues.

When control lever 64 is retarded in a counterclockwise direction from one position to another in the O90 range of lever movement, reversal of the above process takes place. Simultaneously, with upward movement of push rod |30, cam |12 reduces the deflection and load of governor spring 328 and governor valve sleeve 320 rises to permit the escape of compressed air at pressure (19M) from bellows |56, through conduit |60, port 340, past valve 334, through port 344 and conduit 346 to the outside atmosphere. Pressure (pM) is thereby reduced and servo valve |44 and piston |48 rise. The rise of piston |48 decreases the force of spring 2 I4 on power piston |28 so that piston |28 also rises, elevating the left end of lever |28. At the same time, the elevation of push rod |30 and finger 2|6 raises the right end of lever |28, so that main servo valve |24 is raised. This reduces the pressure in chamber |42, permitting piston |96 to rise and move valve 88 in a closing direction, thereby decreasing fuel flow and engine speed.

With the position of control lever 't4 fixed, the engine speed may vary owing to variations in fuel quality, combustion temperatures, or other factors over which the barometric or thermal control systems may or may not have control.

When, under such circumstances, the engine speed increases Without any change in position of control lever 64, valve sleeve 320 is raised from its neutral position in respect to land 334 of valve 332 and, as previously shown, pressure (pM) is thereby decreased. The main power piston rises and the process of reducing the variable control pressure (pc), fuel ow, and hence engine speed, follows, until the desired value of speed is restored. When the engine speed decreases at a xed position of the control lever, the process of increasing the fuel ow to restore the desired value of engine speed is substantially the reverse of the process which occurs upon overspeeding.

As control lever 64 is moved between its 90 and 100 quadrant positions, the throw of cam |72 remains substantially constant at a maximum value. The engine speed therefore has a substantially constant maximum value when the lever is in its 90-100 range of travel. Within this range, however, the throw of cam |32 continues to increase to a maximum value corresponding to the extreme or 100 position of lever travel. Response of the combined manual and speed control systems to movement of the control lever in this ten-degree range is similaito that in cases previously explained in which the fuel flow and engine speed vary as a function of both the manual and speed control systems, except that the speed control system is effective to override the manual control system to a relatively greater extent in order to maintain a substantially constant maximum value of speed. As the fuel flow is increased at constant maximum engine speed, the engine torque and hence the brake-horsepower increase, the maximum brakehorsepower being developed at the 100 lever position Aiternatively, if desired, the throw of cam |12 may be made to increase throughout the 100 range of lever movement.

Coordination of the manual, parametric, and speed control systems The manual, barometric and speed contro1 systems cooperate to regulate the fuel iiow and engine speed as a function of manual control, oompressor discharge pressure (pD), and engine speed. The operation of the manual controy system was previously explained on the assumption of a fixed position of circular bearing 208 in lever mechanism |34. 'The barometric and speed control systems vary 'the position of bearing 208, thereby varying the downward force on main power piston i213 and hence varying the value of the variable contro1 pressure (pc) in chamber |42 and the opening of valve 88.

As bearing 208 moves leftward, corresponding to downward movement of the barometric power piston Ult produced by an increase of the oompressor discharge pressure (pn or pM), the force transmitted by the bearing from spring 2|@ and lever 2% to lever 2F22 and rod 290 is increased so that the value of pressure (pc) corresponding to the position of main control shaft 60 increases. Conversely, as bearing 20a moves rightward, corresponding to decrease of the pressure (11D or pM), the pressure (pc) decreases.

It is thus seen that the value of the variable control pressure (pe) corresponding to any given position of the manual control lever 64, Fig. l, dedepends upon the barometric control system, the pressure (pc) increasing as `the pressure (pD or pM) in bellows |56 increases, as when the vengine speed increases, the speed of ight increases, or as the altitude of flight decreases.

Since the compressor discharge pressure (10D) increases as the engine speed increases, it follows that the barometrc contro1 system controls the rate of acceleration when the engine control lever is advanced. On movement of the lever, within the iirst range of operation, from one position to another corresponding to a higher rate of speed, the initial value of the pressure (pc) corresponds to the initial value of the pressure (10D) -or pM) and to the initial lever position. The increase of pressure (pc) due to movement of the manual control is relatively rapid, but the corresponding, increase due to increase of the pressure (pD .or pM) occurs only as the engine speed increases and as the barometric and speed control systems respond to such speed increase. The barometric control system thus serves to control acceleration and deceleration of the engine.

When the entering air density increases as a function of increasing speed and decreasing altitude of flight, bearing 208 moves leftward to increase the pressure (pc) and the fuel iiow as above explained. Conversely, as the iiight speed decreases and the altitude increases, the compressing discharge pressure (pD) or (pM) decreases and bearing 203 moves rightward to decrease the pressure (pc). The barometric contro1 is sometimes descriptively referred to as the altitude control, and cam |52 is customarily contoured with closer regard to altitude compensation than to acceleration control, particularly since the latter is accomplished to some extent by chopper valve eilt.

rEhe contour or the barometric cam |52 is made to provide a desired position of bearing 20B for every value of the compressor discharge pressure (pM). in operation, in which the temperature control system is ineiective and the control apparatus is in equilibrium, the fuel low is dependent upon: (l) the manual and barometric control systems; and (2) the speed control system which overrides these combined systems to reduce the fuel flew, previously explained.

Thermal control system The thermal control system is essentially a means for overriding the manual control system to reduce the fuel iicw and engine speed when a predetermined limiting Value of temperaeeded.

Thermal control 1|), as shown in Fig. 2, in-

cludes a body 36d on which is xed a thin walled tube 356 which has its right-hand end closed. i Body 354 is provided with a pair of chambers 363 seated in aperture 3l@ to prevent iiow from chamber 368. 'Iube 356 and rod 316 are made from materials having substantially diierent coefficients of thermal expansion, so that when the tube and rod are heated, the tube expands faster than the rod, 'the thermal control generally being made so that the valve remains closed until the predetermined limiting temperature is exceeded. The control is installed with tube 3st exposed to the engine temperature, as in the tail pipe Sli of the engine of Fig. 1. Then, when the tail pipe temperature exceeds the limiting value, the valve opens to permit the flow of compressed air from conduit |14 through chamber 368, past valve 318 to the outside atmosphere. The pressure (pD or pM) in conduits |1il, it and the interior of bellows |56, is decreased as valve 318 opens.

When valve 314 in thermal control 1B is closed, the pressure in conduits |14, i60 and the interior of bellows |56 is maintained at pressure (pn or pM), but when the limiting engine temperature is exceeded, valve 318 opens and compressed air escapes from bellows |56, at a rate corresponding to the degree of excess temperature, with corresponding reduction of the pressure (10D or pM) therein. rlihis decrease in pressure (pD or pM) causes a decrease of the Value of the control pressure (pc), as previously explained, and the fuel flow and engine speed are decreased below the values corresponding to the manual control setting. The flow remains at its decreased rate until the engine temperature is reduced to or slightly below the limiting value, whereupon thermal control valve 314 closes and normal operation is resumed.

The thermal control used in the fuel control.

apparatus need not necessarily be the particular type shown, since any temperature responsive device functionally equivalent to control 1d may be employed if desired.

The manner in which the manual and baro'- lmetric control systems are coordinated in order to control the pressure (pc) and the fuel flow as joint functions of the engine control lever and the compressor pressure differential is apparent from the foregoing. The speed and thermal control systems are shown to be override controls for preventing excessive engine speed and temperature.

Fuel Valve 88 is rigidly attached to piston ii so that the degree of opening through fuel ports S6 and 3% is proportional to the downward travel of piston its. Since valve |66 maintains a constant metering head on valve 8S, regardless of variations in pressures (p1) and (p2), the rate of fuel iiow to the engine is a function of the position or valve tt, as determined by piston llii, which in turn is controlled by control pressure (pc). The lower end of cylinder |li2 below piston |96 is vented to reservoir 1li by conduit ttt, so that the lower side of piston 96 is subjected to the substantially constant pressure (p) in reservoir'l. At the same time, the upper end of piston M8 (which is of the same effective area as the loi-ver end of piston its) is also subjected to the pressure (p) in reservoir 1Q. Since the upward thrust of pressure (p) on piston ist is always balanced byv the downward thrust of pressure (p) on piston |28, the net effect of pressure (p) on the control pressure (pc) in chamber m2 is nil.

The force of spring 3B which biases valve @il towards its seat, is Varied by a'movable seat Si which is perforated to permit maximum unrestricted fuel iiow and is raised or lowered by an adjusting screw Q3, threaded through the bottom wall of casing 12 and locked in adjusted position by a lock nut S5. Spring S9 is adjusted so as to permit valve 8S to commence to open when control pressure (pc) in chamber idr is at its minimum value, corresponding to the condition of engine operation which requires the minimum fuel flow. The calibration of spring S9 is such as to cause valve 88 to vary the opening through ports 84 and Sli in a predetermined ratio to the ccntrol pressure (pc) in chamber |42, so that the rate of fuel ow is in accordance with a predetermined ratio to control pressure (pc). Since the control pressure (pc) is regulated by the combined actions of the manual control, barometric control, speed control and temperature control systems, it follows that the fuel flow to the engine, and hence engine speed, is controlled by the position of the manual control lever and is compensated by the barometric, speed, and temperature control systems for variations in engine operating conditions.

The terms and expressions used herein are employed for purposes of description and not of limitation, and have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed.

I claim: l

l. For an internal combustion engine having a manual control lever, in combination with a constant delivery fuel pump connected by a conduit to said engine, a fuel control apparatus connected in fuel flow series with said conduit and comprising: a valve in fuel flow series in said apparatus for regulating the fuel flow to said engine, means for maintaining a constant metering head on said valve, irrespective of variations in fuel pressure in said conduit, means responsive to changes in barometric pressure for modifying the opening of said valve in accordance with said changes, so as to prevent variations in engine speed due to variations in barometric pressures, and means for varying the opening of said valve in accordance with any movement of said lever, whereby the rate of fuel flow to said engine and engine speed is determined by said lever in any operating position thereof.

2. A fuel control apparatus as in claim 1, having means, responsive to the speed of said engine, for varying the opening of said valve so that the rate of fuel flow to said engine is modified in accordance with engine speed.

3. A fuel control apparatus as in claim 2, Wherein said speed responsive means includes means to adjust the rate of fuel flow to said engine so that the speed of said engine coincides with a selected in said speed responsive means includes means A to limit the fuel flow to said engine so that said speed cannot exceed a selected maximum limit, regardless of the position of said control lever.

5. A fuel control apparatus as in claim 4, having means, responsive to the movement of said control lever, for increasing the fuel flow to said engine, beyond the now corresponding to said selected maximum engine speed, so that the torque and power output of said engine may be further increased by moving said control lever, without exceeding said maximum speed,

6. A fuel control apparatus as in claim 1, having means, responsive to an air pressure in said engine, for varying the opening of said valve so that the rate of fuel flow to said engine is modified in accordance with variations in said air pressure.

7. A fuel control apparatus as in claim 6, wherein said air pressure responsive means includes means to adjust the rate of fuel flow to said engine so that the speed of said engine corresponds to any operating position of said control lever, and is substantially constant, irrespective of variations in said air pressure.

8. A fuel control apparatus as in claim l, having means, responsive to atmospheric density imf mediately outside said engine, for varying the opening of said valve so that the rate of fuel ow to said engine is modified in accordance with variations in said density.

9. A fuel control apparatus as in claim 8, wherein said density responsive means includes means to adjust the rate of fuel ow to said engine so that the speed of said engine corresponds to any operating position of said control lever, and is substantially constant, irrespective of variations in said density.

l0. A fuel control apparatus as in claim lI wherein said valve is a balanced disc valve of the poppet type.

1l. A fuel control apparatus as in claim 2, having means, responsive to a temperature in said engine, for varying the opening of said valve so that the rate of fuel flow to said engine is modifled in accordance with said temperature.

l2. A fuel control apparatus as in claim l1, wherein said temperature responsive means includes means to limit the fuel flow to said engine so that said temperature can` never exceed a predetermined maximum limit under any engine operating conditions.

13. A fuel control apparatus as in claim 1l, wherein said temperature responsive means includes means to limit the fuel flow to said engine so that the speed of said engine cannot exceed a speed which causes said temperature to rise above a selected maximum limit, regardless of the position of said control lever.

14. A fuel control apparatus as in claim 2, having means, responsive to an air pressure in said engine, for varying the opening of said valve, irrespective of the position of said manual control lever, so that the rate of fuel flow to said engine is always modified in accordance with variations in said air pressure, whereby said engine speed coincides with a selected speed corresponding to any selected position of said control lever, and is substantially constant, irrespective of vari ations in said air pressure and in other engine operating conditions which tend to vary engine speed.

i5. A fuel control apparatus as in claim l, having means, responsive to an air pressure in said engine and to atmospheric density immediately outside said engine, for varying the opening of said valve so that the rate of fuel flow to said engine is modified in accordance with variations in said air pressure and atmospheric density, whereby said engine speed coincides with a selected speed corresponding to any selected position of said control lever, and is substantially constant, irrespective of variations in said air pressure and atmospheric density which tend to vary engine speed.

i6. A fuel control apparatus as in claim 2, having means, responsive to atmospheric density immediately outside said engine, for varying the opening of said valve so that the rate of fuel iiow to said engine is modified in accordance with said density, whereby said engine speed coincides with a selected speed, corresponding to any selected position of said control lever, and is substantially constant, irrespective of variations in said density and in other engine operating conditions which tend to vary engine speed.

17. A fuel control apparatus as in claim 2, having means, responsive to a temperature in said engine, for varying the opening of said valve so that the rate of fuel flow to said engine is modiiied in accordance with said temperature, whereby said engine speed coincides with a selected speed, corresponding to any selected position of said control lever, and is substantially constant, irrespective of variations in said temperature and other engine operating conditions which tend to vary engine speed.

18. A fuel control apparatus as in claim 6, having means, responsive to a temperature in said engine, for varying the opening of said valve so that the rate of fuel flow to the engine is modified in accordance with variations in said air pressure and said temperature, whereby said engine speed coincides with a selected speed, correspending to any selected position of said control lever and is substantially constant, irrespective of variations in said air pressure and said temperature.

19. A fuel control apparatus as in claim l, having means, responsive to engine speed, to an air pressure in said engine, to atmospheric density immediately outside said engine, and to a temperature in said engine, for varying the opening of said valve so that the rate of fuel ilow to the engine is modified in accordance with variations in said engine speed, said air pressure, said atmospheric density and said temperature, whereby said engine speed coincides with a selected speed, corresponding to any selected position of said control lever, and is substantially constant, irrespective of Variations in said air pressure, said atmospheric density, said temperature, and other engine operating conditions which tend to Vary engine speed.

20. A fuel control apparatus according to claim 1 wherein said control lever acts on said valve through the medium of fuel supplied by said fuel pump.

21. A fuel control apparatus according to claim 2, wherein said speed responsive means acts on said valve through the medium of fuel supplied by said fuel pump.

22. A fuel control apparatus according to claim 6, wherein said air pressure responsive means acts on said valve through the medium of fuel supplied by said fuel pump.

23. A fuel control apparatus according to claim 8, wherein said atmospheric density responsive means acts on said valve through the medium of fuel supplied by said fuel pump.

24. A fuel control apparatus according to claim 1l, wherein said temperature responsive means acts on said valve through the medium of fuel supplied by said fuel pump.

25. A fuel control apparatus as in claim 14, wherein said speed responsive means acts on said valve through the medium of said air pressure responsive means.

26. A fuel control apparatus as in claim 15, wherein said atmospheric density responsive means and said air pressure responsive means act on said valve through the medium of a combined operating mechanism.

27. A fuel control apparatus as in claim 18, wherein said temperature responsive means acts on said valve through the medium of said air pressure responsive means.

28. A fuel control apparatus as in claim 19, wherein said engine speed responsive means, said air pressure responsive means, said atmospheric density responsive means and said temperature responsive means, all act on said valve through the medium of a common pressure chamber in said apparatus which is supplied with fuel by said fuel pump.

29. A fuel control apparatus as in claim 28, including means for coordinating the actions of said engine speed responsive means, said air pressure responsive means, said atmospheric density responsive means, said temperature responsive means, and said manual control lever, to create a combined control pressure in said chamber, which pressure regulates the opening of said valve, so that the fuel iiow to said engine and consequent engine speed are controlled by any selected position of said lever, and said engine speed is substantially constant, irrespective of variations in said air pressure, said atmospheric density, said temperature and other conditions of engine operation which tend to vary engine speed, at any selected position of said control lever.

30, For an internal combustion engine having a manual control lever, in combination with a constant delivery fuel pump connected by a conduit to said engine, a fuel control apparatus connected in fuel flow series With said conduit and comprising: a valve in fuel flow series in said apparatus for regulating the fuel flow to said engine, means for maintaining a constant metering head on said valve, irrespective of variations in fuel pressure in said conduit, and means, actuated by an hydraulic control pressure responsive to engine speed, for varying the opening of said valve so that said speed is maintained at a constant value, corresponding to any operating position of said control lever, irrespective of varying engine operating conditions which affect said speed.

31. For an internal combustion engine, in combination with a constant delivery fuel pump connected by a conduit to said engine, a fuel control apparatus connected in fuel flow series with said conduit and comprising: a Valve in fuel now `series in said apparatus for regulating the fuel .flow to said engine, means for maintaining a constant metering head on said valve, irrespective of variations in fuel pressure in said conduit, and means, actuated by an hydraulic control pressure responsive to the rate of air flow through said engine, for varying the opening of said valve so that the rate of fuel ow bears a predetermined ratio to the rate of said air now under varying engine operating conditions.

32. For an internal combustion engine, in combination with a constant delivery fuel pump connected by a conduit to said engine, a fuel control apparatus connected in fuel flow series with said conduit and comprising: a valve in fuel flow series in said apparatus for regulating the fuel flow to said engine, means for maintaining a constant metering head on said Valve, irrespective of variations in fuel pressure in said conduit, and means, actuated by an hydraulic control pressure responsive to an air pressure in said engine, for varying the opening of said valve so that the rate of fuel flow is modified in accordance with variations in said pressure and thereby com pensated for such variations.

33. For an internal combustion engine, in combination with a constant delivery fuel pump connected by a conduit to said engine, a fuel con trol apparatus connected in fuel flow series with said conduit and comprising: a valve in fuel flow series in said apparatus for regulating the fuel flow to said engine, means for maintaining a constant metering head on said valve, irrespective of variations in fuel pressure in said conduit, and means, actuated by an hydraulic control pressure responsive to the density of the air entering said engine, for varying the opening of said Valve so that the rate of fuel flow is modied in accordance with variations in said density and thereby compensated for such Variations.

34. For an internal combustion engine, in combination with a constant delivery fuel pump connected by a conduit to said engine, a fuel control apparatus connected in fuel ow series with said conduit and comprising: a valve in fuel flow series in said apparatus for regulating the fuel flow to said engine, means for maintaining a constant metering head on said valve, irrespective of variations in fuel pressure in said conduit, and means, actuated by an hydraulic control pressure re sponsive to a temperature in said engine, for varying the opening of said valve so that the rate of fuel flow is modified in accordance with variations in said temperature, whereby said temperature cannot exceed a predetermined maximum safe value.

35. For an internal combustion engine, in combination with a constant delivery fuel pump connected by a conduit to said engine, a fuel control apparatus connected in fuel flow series with said conduit and comprising: a valve in fuel flow series in said apparatus for regulating the fuel How to said engine, means for maintaining a 23 constant metering head on said valve, irrespective of variations in fuel pressure in said conduit, and means, actuated by an hydraulic control pressure responsive to engine speed, for Varying the opening of said valve so that the rate of fuel flow is regulated in accordance with engine speed and limited so that said speed cannot exceed a predetermined maximum safe value.

36. For an internal combustion enging having a manual control lever, in combination with a constant delivery fuel pump connected by a conduit to said engine, a fuel control apparatus connected in fuel ovv series with said conduit and comprising: a valve in fuel flow series in said apparatus for regulating the fuel flow to said engine, means for maintaining a constant metering head on said valve, irrespective of variations in fuel pressure in said conduit, and means, actuated by an hydraulic control pressure responsive to engine speed and to the rate of air flow through said engine, for varying the opening of said valve to regulate the rate of fuel flow in accordance with said speed and rate of air flow so as to maintain a constant engine speed, corresponding to any operating position of said control lever, irrespective of engine operating conditions that affect said speed and rate of air ow.

37. For an internal combustion engine, in combination with a constant delivery` fuel pump connected by a conduit to said engine, a fuel control apparatus connected in fuel fiow series with said conduit and comprising: a valve in fuel flow series in said apparatus for regulating the fuel flow to said engine, means for maintaining a constant metering head on said valve, irrespective of variations in fuel pressure in said conduit, and means, actuated by an hydraulic control pressure responsive to any movement of said lever, to engine speed and to an air pressure in said engine, for varying the opening of said valve so that the rate of fuel flow is controlled by any position of said lever and is modified in accordance with variations in said speed and pressure and thereby compensated for such variations.

38. For an internal combustion engine having a manual control lever, in combination with a constant delivery fuel pump connected by a conduit to said engine, a fuel control apparatus connected in fuel flow series with said conduit and comprising: a valve in fuel 110W series with said apparatus for regulating the fuel flow to said engine, means for maintaining a constant metering head on said valve, irrespective of variations in fuel pressure in said conduit, and means, actuated by an hydraulic control pressure responsive to any movement of said lever, to engine speed, to an air pressure in said engine, and to the density of air entering said engine, for varying the opening of said valve so that the rate of fuel flow is controlled by any position of said lever and is modified in accordance with variations in said speed, pressure and density and thereby compensated for such variations.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,219,994 Jung Oct. 29, 1940 2,224,472 Chandler Dec. l0, 1940 2,341,257 Wnsch Feb. S, 1944 2,422,808 Stokes June 24, 1947 2,469,678 Wyman May 10, 1949 2,470,382 Vanni May 17, 1949 2,515,074 Bobier June 11, 1950 2,531,780 Mock Nov. 28, 1950 2,573,724 Neal Nov. 6, 1951 2,581,276 Mock Jan. 1, 1952 2,604,756 Greenland July 29, 1952 2,622,393 Edwards et al. Dec. 23, 1952 FOREIGN PATENTS Nambe; Country Date 603,884 Great Britain June 24, 1948 

